1. Field of the Invention
This invention relates to antimicrobial compositions, furthermore relates to antimicrobial agents containing the composition as active ingredient particularly useful for the prevention and treatment of opportunistic infectious diseases.
2. Description of the Prior Art
Methicillin-resistant Staphylococcus aureus (hereinafter abbreviated as MRSA) includes Staphylococcus aureus strains that are resistant to various antimicrobial agents such as methicillin, cephem antibiotics, and so on. The strains have recently been noted as pathogens of nosocomial infections such as opportunistic infections, and countermeasures to these infectious diseases of nowadays are serious problems for medical care. Some MRSAs are resistant not only to cephem antibiotics but also to chloramphenicol antibiotics.
Antimicrobial activity of peptides isolated from the hemocytes of horseshoe crabs against Gram positive and negative bacteria, and fungi have been known. However, these peptides do not exhibit sufficient antimicrobial activity by single administration. For example, the minimum inhibitory concentration (MIC) against Staph. aureus is reported to be 3.1-6.2 .mu.g/ml. Doses of these antimicrobial peptides sufficient to induce antimicrobial activity causes toxic side effect. The peptides are expensive and not easily available as they are isolated from natural horseshoe crab. Therefore, antimicrobial peptides isolated from the hemocytes of horseshoe crab could not easily be used as antimicrobial agents.